The present invention is related to movable insulation, and more specifically to a method and apparatus for fabricating expandable honeycomb insulation panels of a flexible thin film plastic material and the product produced according to such method.
With the advent of the energy shortages experienced over the last decade, there has been a renewed interest in energy conservation applications related to heat gains and losses through poorly insulated wall areas, such as windows and the like. One of the basic tenents of passive solar energy saving designs for building is that large generally south facing windows can be used to gain heat during sunny winter days. However, large windows are also responsible for heat loss during cold winter nights due to re-radiation of the heat from the interior of the house through the windows to the colder exterior. On the other hand, during hot summers, it is desirable to keep the heat from the sunlight during the day out of the interior of the house and to allow the heat in the house to radiate to the outside during the nights. Therefor, in order to take optimum advantage of the heating and cooling cycles of the sun or absence thereof during day and night periods, it is necessary to be able to move insulation in place over the windows or to retract it at appropriate times to allow the transfer of heat therethrough or to prohibit the transfer of heat therethrough as desired. This need for movable insulation panels has resulted in a renewed interest in the use of honeycomb structured panels for movable insulation purposes since they contain numerous individual dead air space cells and are readily expandable and contractable. However, it is also necessary to have a material that reflects sunlight and is able to maintain its effectiveness, shape, structural rigidity and appearance through wide ranging temperature variations and over long periods of use. During hot summer days when the panel is in place over the window, temperatures can reach well over 100 degrees F. Alternately, on cold winter nights, the temperatures can be quite low.
In other kinds of movable insulation structures, it has been found that a thin film polyester plastic material, commonly known by the trademark Mylar, has suitable characteristics for movable insulation applications. It can withstand the temperature variations required, reflective coatings can be applied on the surfaces thereof, it has the required longevity, and it is relatively inexpensive. However, past efforts to fabricate honeycomb movable insulation panels from thin film polyester or Mylar material have left much to be desired. For example, it has been found to be quite difficult to fabricate on a mass production basis clean cut, uniform and neat appearing panels with no wrinkles or warps to detract from the appearance thereof or to interfer with the insulating function of the panels. Further, mechanical folds and creases in the plastic film tend to lose their sharpness and sag or become rounded over time. The failures are particularly troublesome when the material is subject to high temperatures during hot summer applications, since the molecular bias of the plastic film material is toward the flat configuration of which is was manufactured. Prior attempts to set the folds or creases on the edges by pressure and by heating have not been successful because these methods cause internal stresses that result in warps and wrinkles. Further, prior art attempts at stacking adjacent tubular layers of the thin film plastic material to form the panels have also been generally unsatisfactory in that they result in wrinkles and warps, and uneven lines. Some prior attempts have also included exceedingly cumbersome machinery having many strips of material running simultaneously.